1. Technical Field
The invention relates generally to integrated circuit (IC) design, and more particularly, to a device and method for determining thermal absorption variations across an IC chip.
2. Background Art
In both the 90 nm and the 65 nm technologies and beyond, large variations in the on currents and/or off currents of components/parts may exist within a single IC chip. Factors contributing to such variations include, among others, differences in the thermal absorption on/of parts (at different locations) of a chip, gate length/width variations, field effect transistor (FET) width variations, etc. In the 90 nm and the 65 nm technologies, the thermal absorption variation has become one of the dominant mechanisms for the variations in the on currents and the off currents.
As the on/off current variations are caused by various factors, it is desirable to separate and quantify the contributions of each single factor. It is also desirable to track the variation of a contributing factor itself. Technologies have been developed to monitor the total threshold voltage variations of the FETs using, e.g., a frequency gradient with respect to the voltage of an on-chip ring oscillator. Gate width/length variation may also be detected using, e.g., Nova™ NanoSEM available from FEI company.
However, according the present state of the art technologies, no satisfactory solution exists for determining/monitoring the thermal absorption variations across an IC chip. As such, there is a need for such a solution.